This invention relates to an armature winding method and apparatus and especially to the winding of armatures for electric motors of the type having an armature core and a commutator mounted in spaced relation on an armature shaft and wherein the commutator comprises a plurality of circumferentially arranged bars provided with coil lead wire-receiving slots. This type of commutator is referred to herein as a "slotted commutator".
The present invention is intended for use in association with flier-type armature winding machines, and particularly double flier armature winding machines. In flier-type armature winding machines, the armature coils are wound from continuous lengths of magnet wire having an insulating coating by rotation of fliers from which the insulated magnet wires extend. Lead wire segments between coils are connected to respective associated commutator bar slots. A coil lead is connected to, or wedged into, a commutator bar slot by a process called "lead stuffing" in which a segment of the lead is aligned with the commutator bar slot by wire guide tooling and staked or tamped therein by operation of a tamping mechanism. The commutator bar slots are narrower than the diameter of the coil leads so that the act of tamping the leads into the slots causes the insulating coating on the wire to be shaved off by the margins of the bar slots and causes the leads to be deformed in the slots and thereby firmly held in place. (As a separate and subsequent manufacturing step, the coil leads are permanently connected to the commutator bars by a hot staking or fusing operation.)
The invention herein is illustrated as practiced with a double flier armature winding machine. Such machines when used for winding armatures having slotted commutators commonly have wire guide tooling mounted on a commutator shield that completely encircles the commutator of an armature being wound, except that the shield is notched or slotted at two locations, which are usually mutually spaced apart by 180 degrees, to expose a pair of commutator bar slots to enable coil leads to be connected thereto. (As will already be known by those familiar with the art, notches or slots in the shield will be spaced apart by more or less than 180 degrees if the machine is set up to wind armatures having an odd number of slots.) As will be appreciated, the invention is equally applicable to single flier machines, in which the shield would have only one notch or slot. In either case, wires are directed into alignment with the shield notches or slots by wire-guiding surfaces of the wire guide tooling.
At the beginning of an armature winding cycle, a segment of the magnet wire, referred to herein as a start wire, leading to the first coil to be wound by a flier is wedged into a first commutator bar slot. At the end of a winding cycle, a finish wire extending from the last coil wound is also wedged into a commutator bar slot over a start wire therein. When using a single flier armature winder, all of the coils are wound from a single strand of wire, and the single finish lead is wedged into the same slot as the single start lead. In double flier armature winding machines having two fliers, there are two start and two finish wires. The finish wire generated by one of the fliers is placed over the start wire generated by other of the two fliers, and vice versa.
Leads between successively wound coils are tamped one above the other into their respective commutator slots. Thus, the wire leading to a flier from the last turn of one coil is aligned with or placed in a commutator slot by appropriate rotation of the flier, such lead usually then being tamped therein. The wire segment leading to the flier from the commutator slot is usually then bent or looped on itself, by further movements of the flier, aligned with or placed into the same slot, and tamped therein. The loops formed in the wire segments between the two leads become wasted wire which usually must be removed from the commutator by a subsequent processing operation. These loops are preferably quite small in order to minimize the amount of wasted wire and to simplify or eliminate the need to remove the excess wire forming the looped portions. However, with existing machines, the loops are usually larger than desirable. The amount of excess wire becomes significant when taking into account that there are wasted wire segments between each pair of wound coils and the great number of armatures that are manufactured each year.
When winding an armature, the winding of the armature coils and the connection of the lead wires to the commutator bars takes place while the armature is held by a chuck or collet clamp at a winding station and properly positioned with respect to the fliers. The chuck or collet clamp is rotatable so that the armature can be rotated or indexed as needed to place successive pairs of armature core slots in position to receive coils wound by the fliers and to locate the appropriate commutator bar slots in position to receive wire leads.
Between the winding of successively wound armatures, the magnet wire segments leading from the finish wires of the newly wound armature are usually gripped by wire clamps and the short segments of wire between the finish wires and the clamps are severed so that the wound armature is cut free from the wire segments leading to the fliers. The wound armature is then removed from the winding station and replaced by an unwound armature and, while the wire clamps retain their grip on the wire segments leading to the fliers, the start wires are tamped into wire lead-receiving slots of the unwound armature. At that time, or shortly thereafter, the clamped wire segments are cut free from the start wires of the armature now located in the winding station. The processes for cutting the clamped wire segments free from the finish and start wires are known as "lead trimming" or "lead cutting".
In a lead trimming or cutting method that has been used successfully, a finish wire is severed closely adjacent its associated commutator bar slot by clamping the finish wire after it is wedged into the appropriate bar slot, and then by rotating the armature to bend the finish wire about an edge of the commutator that partly defines the slot in which it is wedged. As a result, the finish wire is subjected to a high concentration of stress at the edge of the commutator bar slot and ultimately breaks at that edge. The wire leading to the flier remains clamped while the newly wound armature is removed from the winding machine and replaced by the next unwound armature. After the usual index to properly locate a slot of the unwound armature in position to receive a wire lead, the flier is rotated and the tamping mechanism operated to wedge a start wire into a commutator bar slot. Rotation of the flier mechanism is interrupted and the armature again rotated so that the clamped portion of the wire is stretched and severed adjacent the start wire slot.
Although prior flier-type machines used for winding armatures having slotted commutators in accordance with the methods described in the preceding paragraph are generally satisfactory, they have certain drawbacks. For one, the known wire clamp mechanisms and clamping methods are typically relatively complex and expensive. In addition, the prior machines have relatively complex assemblies or mechanisms for guiding and tamping the wires into the commutator bar slots. These are difficult to retool and set up properly when there is a change in the construction of the armatures to be wound. Moreover, the existing tamping mechanisms can be difficult to adjust and may require frequent readjustment.